Imaging of specimens at optimized low and very low energies in scanning electron microscopes

Abstract

Summary:The modern trend towards low electron energies in scanning electron microscopy (SEM), characterised by lowering the acceleration voltages in low-voltage SEM (LVSEM) or by utilising a retarding-field optical element in low-energy SEM (LESEM), makes the energy range where new contrasts appear accessible. This range is further extended by a scanning low-energy electron microscope (SLEEM) fitted with a cathode lens that achieves nearly constant spatial resolution throughout the energy scale. This enables one to optimise freely the electron beam energy according to the given task. At low energies, there exist classes of image contrast that make particular specimen data visible most effectively or even exclusively within certain energy intervals or at certain energy values. Some contrasts are well understood and can presently be utilised for practical surface examinations, but others have not yet been reliably explained and therefore supplementary experiments are needed.

A comparison of conventional Everhart‐Thornley style and in‐lens secondary electron detectors—a further variable in scanning electron microscopy

“…The sensitivity of the “SE” image to the range of SE energies being collected is of increasing interest and attention. These data are in accord with the ultra‐low energy imaging techniques (Mullerova, 2001) and ongoing in‐depth studies of the energy‐filtering capabilities of the TLD detectors (Kazemian et al ., 2006; Rodenburg et al ., 2010).…”

Practical method for high‐resolution imaging of polymers by low‐voltage scanning electron microscopy

“…The use of low-energy electron probes leads to a decrease in the electron-specimen interaction volume and increased sensitivity to surface detail. Moreover, stabilization of the surface potential may occur at low accelerating voltages (Müllerová 2001). Charging of uncoated insulating specimens may therefore be reduced, particularly close to the crossover voltage, E 2 , which corresponds to the beam energy, at which the number of incident electrons equals the number of exiting electrons and the surface potential reaches a minimum (Reimer 1985).…”

Image Contrast in Energy-Filtered BSE Images at Ultra-Low Accelerating Voltages

“…By applying the formula (2) and (3) to the formula (1), N e can be calculated by: (5) where I p is the probe current, e is the electron charge, and τ is the dwell time. there are a few data points that show a deviation from the reference data at the higher landing energy.…”